to extend the life of your engine, you will first want to start running a high-quality synthetic oil - probably 20w40 or 20w50 - change it frequently too, my preferred oils are Castrol and Mobil 1
the engine block design is quite good actually (the same block/engine is used in some custom aeroplanes, in stock turbo form) - cylinder walls are consiterably thicker than most other cars of that era, and the block is aluminum alloy, not strait aluminum (that simply wouldn't work due to aluminum's thermal expansion rate) - the problem is that the turbo takes all its coolant/oil from the #3 cylinder instead of from a centralized point, like later turbo soobs - it might be good if you could plumb the coolant into the heater circuit instead of the #3 cylinder
NEVER OVERHEAT THE ENGINE - if the cooling system dies, so does your engine - because of the afforementioned coolant flow issue, the headgaskets will blow due to the excessive heat on #3 in very short order - HG's are the biggest problems on these engines
intercooler would be good for the engine - FI pressure & all is a nonissue if you injectors/FI system is stock (intercooler won't make a difference in the FI system) - and don't hit the fuel cutoff point (the overboost protection system) - a good idea would be to idle the engine ~30 seconds or more before cutting it off to allow the turbo to cool down and prevent "coking" of the oil in the turbocharger - subaru actually recommends this in their owner's manual
BOV is an OK idea, just make sure it vents to the intake duct between the MAF and turbo intake rather than the atmosphere - sometimes it does work venting to the atmosphere, but usually it will confuses the computer and make it go super rich and stumble... besides, it is sloppy to vent it to the atmosphere as the intake is supposed to be closed after the MAF - BOV's protect the turbo, when the throttle is released quickly, not the engine itself - and they make ricers happy (along with their plastic bodykit) - the engine itself will not see any difference one way or the other, at a MAX of 9psi boost stock, I am not sure how important it is for the turbo anyway, unless you add a IC, then it will probably be more important
if you search EA82T, you will probably find more info that you can sort through on this subject